How to properly run a C30 with 435hp for longevity?

[dbsea]

thanks for all the words of wisdom. I'm still "new" to the boat (October), and definitely still in the learning phase. Even if I don't intend to keep the boat forever (probably 5-10 years), I very much operate from a pride of ownership mentality, and when I sell the boat, I appreciate that the new owner will know that I've taken good care of it. I'm still experimenting with the trim tabs, rpm speed, etc. to find the sweet spot. Will probably have it dialed in just in time for summer.

 

[S. Todd]

If one of the big concerns is the amount of fuel that is run through the engine, rather than the actual hours, and our boats have fairly consistent miles per gallon numbers, if my goal is to go from point A to point B, I am not sure it makes a whole lot of difference whether I travel at 13 miles per hour or 20 miles per hour (90% of max RPM on our D-4 320). I may get more hours on the engine going at a slower speed, but because it takes more hours to get there, l am not sure what I have gained. I personally don't cruise open water above 90% of WOT RPM, but more typically do 80%. Our average when you take into account all travel including rivers, marinas, rough water, canals, etc. ends up with an average gallons per hour burn rate of much less than what the fast cruise rate is. (Prior to becoming Ranger Tug owners we cruised the same areas of the Great Lakes in Sea Ray boats and our typical trips put less hours on the gasoline stern drives because the open water cruising, unless it was rough, typically took half the time.)

 

[FlyMeAway]

The total job for the engine refits with new long blocks and exchanger rebuilds plus parts and labor was just short of 100K.

Either this is for all 4 engines across two boats, or these engines required sawing out half the fiberglass, or I call bullshit.

A brand-spanking-new D4-300 is about $12k, usually +/- 10% if you consider discounts and freight. A full engine replacement can be done in a good yard for $3-5k of labor, maybe $6k if the yard is slow. A D6-435 is around $18k +/-, so not that much more.

A full, ground-up engine replacement (not a rebuild) on our boats is therefore around $20-24k. Every 5 years, that's a stretch; every 10 years, it isn't too surprising. I do know boaters who have 7000+ hours on a D4 and run it at 70-80% WOT (but never more than that at any stretch) for the vast majority of their cruising hours, obsessive about filter change and maintenance. But I have also heard stories like the ones BB Marine suggests. YMMV.

 

[S. Todd]

After reading this thread and questioning whether I push by D-4 harder than recommended I thought I would check my gallons of fuel per hour per liter of engine displacement. My trip averages are in the range of 1.1 gallons per hour per liter and 1.24 gallons per hour per liter. Looks like I am not breaking any fuel burn barriers with my typical cruise over open waters when I stay in that 80% of max RPM range, even when I include the times I exercise the turbo at 100% for short periods.

 

[BB marine]

After reading this thread and questioning whether I push by D-4 harder than recommended I thought I would check my gallons of fuel per hour per liter of engine displacement. My trip averages are in the range of 1.1 gallons per hour per liter and 1.24 gallons per hour per liter. Looks like I am not breaking any fuel burn barriers with my typical cruise over open waters when I stay in that 80% of max RPM range, even when I include the times I exercise the turbo at 100% for short periods.

S. Todd Looks like your operating in a comfortable range. I like to operate my diesels at an average range of 2.0L per gallon. This is a better way of describing operation. The boats are powered with high horsepower engines for a reason. Use the engines power with discretion.

Example: If you are in an open water crossing and you want to cruise fast and run the engine hard for 5 hours burning 12 GPH. Do it! If you then cruise at 2.5 GPH for the next two days 8 hours a day. What was your average GPH burn? This three day trip you burned 100 gallons of fuel. You operated the engine for 21 hours. You have a 3.7 Liter engine. 2 gph per Liter average = 7.4 GPH 100 gallons /21 hours= 4.76 gph. You have operated the engine at an average load of just over 30% load. The D4 and D6 engines are 5 rated engines designed to be operated at a 35% load factor.

This does not mean you should not run them above 35%. We all do and should. What it means is it is not a good idea to operate them at 70% to 80% average because you will reduce the engines operating time in half or more.

When the question is asked what rpm can I run at continuously? The answer as you can see is not simple. To simplify it a rpm is stated. In this thread talking about a 435hp D6 that at 100% load is burning 22 gph I stated 2800 rpm thinking the fuel burn would be about 15 GPH +/- this would be below 70% load and there would most likely be some hours during a cruise that would be below 2800 rpm (no wake areas, channel areas going in and out of anchorages that would lower the average fuel burn. D6 is a 5.5L engine X 2.0 gph per liter you really would want your average GPH to be 11 or less. Realistically 7.7 gph average over all would be the 35% load factor. At this rate the average D6 would operate before needing rebuild for about 5200 hours. Using 40,000.00 gallons burned as a rule of thumb. 40,000 gallons burned is just a average measure used by some diesel engine manufactures.

In the case that

I do know boaters who have 7000+ hours on a D4 and run it at 70-80% WOT (but never more than that at any stretch) for the vast majority of their cruising hours, obsessive about filter change and maintenance

I question this ??? If we are referring to a D4 260 or higher and not a Commercial 175 or 230 D4. I would question a 260hp 300hp or 320hp D4 would operate at 7000 +hours, operated the vast majority of its cruising hours at 70 to 80%. At 60% it would have burned 63000 gallons of fuel ??? That would be amazing!! Now if it was a 230 hp maybe because 100% load on a 230 is less than 70% load of a 320 hp. 70 % load of a 230Hp D4 is = to 50% load of a 320 HP D4. I would still question that.

I would believe 7000 hours is possible the way S.Todd operates his engine in his boat.

A brand-spanking-new D4-300 is about $12k, usually +/- 10% if you consider discounts and freight. A full engine replacement can be done in a good yard for $3-5k of labor, maybe $6k if the yard is slow. A D6-435 is around $18k +/-, so not that much more.

I'm not sure I agree with your assessment. I respect your opinions and comments.

Find me a couple of these D6 completes. I would buy them today! If you can find them available regardless of price.( that seems to be an issue theses days.) Get them for that price you quoted. You can take delivery and double your money and then some. Last time I checked availability for a bobtail D3 220 it listed for 23K. That was a couple years ago. I was looking for a Tug owner that destroyed a D3 because of a timing belt failure. As far as your labor rates. I know in the late 90's I did a re-power in a 42' carver.Twin 5.9 cummins. I remember this job because I questioned why the owner would do this. It billed out at over 60K. That was a lot of $$$ in the 90's. its a lot today! You must have some good cheap yards in your neck of the woods, you're lucky. I would have some of my service work done there at those prices. I received a quote from a Yanmar dealer last fall to do a 1000 hour service on my 2 Yanmar 4HLA STP engines. It was quoted at 8K parts and labor. I did it myself for just under 2K parts. I can't imagine what they would have charged for labor to pull the engines, undress the old blocks, dress the new blocks, send the turbo's and injector pumps out for service, take the after cooler, oil cooler and heat exchangers apart and service , reinstall the engines, align, run the engine in, then inspect valve clearances and adjust injector timing, and commission checks. (all part of a complete engine replacement ). Then add all the parts involved in this job. 5 or 6K Labor in my 34' boat there is no way! Now do this job in a 50' motor yacht and expect it to be done for 5 or 6K ??? I'm sure the folks having this job done at the marina wish they knew your guys!

 

[SJI Sailor]

Great discussion here. I have a related question: how much effect does warm up time have on D4/D6?

An older recommendation for diesel engines was to idle/low power them from start until they reach 100F degrees. Then stay at low power of 1100-1200 RPM until they reach operating temperature of 185F.

I'm not in a hurry so I generally follow this, although I know newer engines are not as fragile. Still, I see many folks who start their engines, leave their slip a minute later, and blast up to 20+ knots as soon as they're out of a marina. That can't be good but how bad is it? Are we again talking about the difference 10k vs 2k hour life, or ... ?

 

[dbsea]

Great discussion here. I have a related question: how much effect does warm up time have on D4/D6?

An older recommendation for diesel engines was to idle/low power them from start until they reach 100F degrees. Then stay at low power of 1100-1200 RPM until they reach operating temperature of 185F.

I'm not in a hurry so I generally follow this, although I know newer engines are not as fragile. Still, I see many folks who start their engines, leave their slip a minute later, and blast up to 20+ knots as soon as they're out of a marina. That can't be good but how bad is it? Are we again talking about the difference 10k vs 2k hour life, or ... ?

I follow this as well. Once I complete my visual inspections when i get on board, starting her up is the first thing I do while i tend to everything else that needs to be done before we set off. I have a long journey from Portage Bay out to the locks, so i'm always at normal operating temp by the time I get there.

 

[FlyMeAway]

@BBMarine, You're right on the cost of the engine, I will give you that -- just called a few places and found a D4-300 bobtail in stock, for ~$30k. When I first started looking at powerboats in 2016, I found a new Volvo D4 bobtail for ~$12k plus freight (I had a confirmed quote as I was looking at a salvage boat that needed a new engine), and more than one place selling them for under $20k. Inflation is a real cluster, apparently.

I can't imagine what they would have charged for labor to pull the engines, undress the old blocks, dress the new blocks, send the turbo's and injector pumps out for service, take the after cooler, oil cooler and heat exchangers apart and service , reinstall the engines, align, run the engine in, then inspect valve clearances and adjust injector timing, and commission checks. (all part of a complete engine replacement ).

No, actually; these are not all things you have to do when you replace one of our engines. My understanding after talking to a dealer is that the turbos, injectors, after cooler, oil cooler, and heat exchanger are all included with Volvo bobtail (basically, the bobtail includes everything between the transmission and the motor mounts; the one thing they weren't sure about was the alternator). It is literally disconnect, remove, install, align, run in. That's the point of the bobtail. On the larger tugs the engine is easy to access and pops right out. 20-40 hour job; I had more than one quote. Labor rates have gone up but hours (I hope!) haven't! I used a $140 an hour labor rate in my estimate, but labor rates are getting closer to $170 in some places, so maybe more.

Of course, a long block replacement (which I think is what you're describing) is going to have a bit more labor than a bobtail engine. But even then, I've seen long block replacement quotes at 35-50 hours. Google corroborates this. Maybe some of the cleaning/service you mention isn't typically included but is just more thorough? I couldn't find long block parts costs. Maybe someone else can provide these?

 

[NewMoon]

Great discussion here. I have a related question: how much effect does warm up time have on D4/D6?

An older recommendation for diesel engines was to idle/low power them from start until they reach 100F degrees. Then stay at low power of 1100-1200 RPM until they reach operating temperature of 185F.

I'm not in a hurry so I generally follow this, although I know newer engines are not as fragile. Still, I see many folks who start their engines, leave their slip a minute later, and blast up to 20+ knots as soon as they're out of a marina. That can't be good but how bad is it? Are we again talking about the difference 10k vs 2k hour life, or ... ?

For our 260hp KAD44P, Volvo factory tech wizards told me not to sit there idling when it was cold (especially before it was well broken in), but to get underway as soon as it was running smooth, then keep it slow (not idling, but rather 6-7 knots, 1200-1400 RPM) until it got to 150 degrees, then power up to planing speed if I wish to. After it was broken in, and warmed up to full normal operating temp (180-185), some idling (for halibut fishing, for instance) would be OK. A few minutes of higher power after longer periods of idling was also recommended.

We found that cruising at 1300-1400 RPM and 6-7-knots kept engine temp up to at least 175, and got to like cruising slow most of the time after our first 2-3 years.

Followed these recommendations for 6,500 hours over 18 years, and it still smoked very little.